The invention relates to an improved recording or reproducing device, such as a magnetic disc.
In recording or reproducing devices using rotary recording media such as magnetic disks, a center core integral with the recording medium is typically fitted on the spindle to load the recording medium.
FIG. 5 shows one example of a magnetic disk cassette of this type. In cassette 1, a center core 2 and a magnetic disk 3 are rotatably incorporated in a jacket 4. When the shutter 5 of cassette 1 is opened, disk 3 is exposed to confront a magnetic head (not shown). Further, in FIG. 5, an elastic member 2a is formed by part of the center core 2. Elastic member 2a is adapted to push the spindle to center the magnetic disk. A PG yoke 6 is buried in the center core 2, in order to detect the rotational phase of the magnetic disk 3.
FIGS. 6 through 8 show one example of a mechanism for mounting the magnetic disk on the spindle. As shown in FIG. 6, a spindle motor 7 is secured to a recording or reproducing body 8, and spindle 7a of the motor 7 has a magnet 9, which is magnetically coupled to a magnetic member fixedly provided on the lower surface of the center core 2. A jacket holder 10 is pivotally mounted on body 8 about a hinge shaft 11. Jacket holder 10 has an opening 10a at one end to receive jacket 4. An outer cover 12 is mounted on body 8 in such a manner that it also pivots about hinged shaft 11. A lock pin 13 is embedded in the front wall 12a of the outer cover 12. A center core pushing member 14 is provided at the central part of the inner surface of the top wall of the outer cover 12. Member 14 is used to push the center core of the magnetic disk to fit the latter on the spindle 7a (as described later).
The operation of the magnetic disk mounting mechanism will be described with reference to FIGS. 7 and 8. First, as shown in FIG. 6, cassette jacket 4 is inserted into holder 10 through opening 10a. Next, cover 12 is swung clockwise about hinge shaft 11 against the elastic force of a spring (not shown), whereby the holder 10 is swung in the same direction about hinge shaft 11. As a result, center core pushing member 14 is abutted against the top surface of the center core 2 to push center core 2 onto spindle 7a. Magnet 9 of spindle 7a attracts a magnetic member 15 of center core 2, to fix center core 2. When, under the condition shown in FIG. 7, the cover 12 is released, the cover 12 is turned slightly counterclockwise by the elastic force of the spring (not shown), and a lock mechanism 16 provided on the body 8 acts on lock pin 13 to lock the latter as shown in FIG. 8. In FIG. 8, center core pushing member 14 retracts above center core 2. Under this condition, spindle motor 7 is energized to turn the magnetic disk 3 so that recording or reproducing is carried out by a conventional magnetic head (not shown). When the lock mechanism 16 is released after recording or reproducing, outer cover 12 and holder 10 are swung counterclockwise by the spring (not shown), thus being restored to the position shown in FIG. 6.
FIG. 9 shows a control circuit for spindle motor 7. The control circuit employs a servo loop which is typical for a recording or reproducing circuit of this type.
A PG pickup 20 confronts PG yoke 6 of center core 2. PG pickup 20 detects the leakage flux of PG yoke 6 to generate a PG pulse S.sub.1 representing the rotational phase of magnetic disk 3. The PG pulse S.sub.1, after being amplified by an amplifier 21, is compared with a reference phase signal (such as a vertical synchronizing signal) S.sub.0 in a conventional phase comparator 22. In phase comparator 22, a trapezoidal wave formed from the reference phase signal S.sub.0 is gated with the PG pulse S.sub.1, so that, when the phase of the PG pulse S.sub.1 leads that of the trapezoid wave, a relatively low error voltage S.sub.2 is outputted, and when the phase of the PG pulse lags that of the trapezoid wave, a relatively high error voltage S.sub.2 is outputted. The error voltage S.sub.2 acts on the spindle motor 7 so that the rotational phase of the magnetic disk 3 is synchronized with the reference phase signal S.sub.0.
The error voltage S.sub.2 is applied to a phase compensating circuit 23 which is either a phase lag circuit or a phase lead circuit. An error voltage S.sub.3 provided at the output terminal of the circuit 23 is added to a speed control signal S of a speed servo system, and the result of this addition is applied to a switch 24.
The speed control signal S.sub.7 is obtained as follows. A frequency signal PG representing the speed of rotation of the spindle motor 7 is obtained from a frequency generator 29, and converted into a DC voltage signal V by a frequency-to-voltage converter 25. The DC voltage signal V is applied to a DC filter 26 to obtain the speed control signal S.sub.7.
Switch 24 is an analog switch which is turned on and off by a motor control signal S.sub.6. That is, when the control signal S.sub.6 is at the level "0", the switch is turned off to interrupt the transmission of the signal S.sub.4. The voltage signal S.sub.4 provided at the output terminal of the switch 24, after being amplified by an amplifier 27, is applied, as a drive voltage signal S.sub.5, to a motor drive amplifier 28. Amplifier 28 is adapted to perform switching (commutation) and amplifying, so that an exciting current I corresponding to the voltage signal S.sub.5 is supplied to the DC spindle motor 7.
In the above-described recording or reproducing device, the center core 2 of the magnetic disk 3 is pushed and fitted on the spindle 7a by the magnetic disk mounting device of FIGS. 6 through 8. Under the condition shown in FIG. 8, the motor control signal S.sub.6 of the level "1" is applied to the switch 24 to excite the spindle motor 7, to thereby rotate magnetic disk 3. After recording or reproducing, the motor control signal S.sub.6 of the level "0" is applied to the switch 24, to interrupt the application of the voltage signal S.sub.4 and accordingly the supply of the exciting current I. Thereafter, the lock mechanism 16 is released to restore the outer cover 12 and the jacket holder 10 as shown in FIG. 6.
Even if the supply of the exciting current I is interrupted by turning off switch 24, the spindle motor 7 is kept turned on for a while by the inertia of the magnetic disk 3, the rotor, etc. Under this condition, sometimes the operator opens the outer cover 12 and the jacket holder 10 while the motor is still being rotated to disengage the center core 2 of the magnetic disk 3 from the spindle 7a, and immediately replaces the cassette 1 with another one and closes the cover 12 and the jacket holder 10, or slightly opens the cover and the jacket and closes them without replacing the cassette 1. In this case, the center core 2 is fitted on the spindle 7a which is still turning. As a result, the surface of the center core 2 which are brought into contact with the spindle 7a and the center core pushing member 14 are greatly worn, which lowers the durability of the center core 2. In addition, it becomes difficult to positively fit or chuck the center core 2 on the spindle 7a. In this case, the disk 3 is rotated while inclined or eccentric, which adversely affects recording or reproducing, thus lowering the quality of the recorded or reproduced picture, for instance, in the case of a still video floppy disk.
In view of the foregoing, an object of this invention is to provide a recording or reproducing device in which the time required for a spindle motor adapted to rotate a rotary recording medium such as a magnetic disk to stop is decreased, so that safe removal of a rotary recording medium from the spindle and mounting another one on it immediately thereafter is possible.
The foregoing object of the invention has been achieved by a recording or reproducing device having recording medium loading means for loading a rotary recording medium by fitting the center core of the rotary recording medium on the spindle of a spindle motor. Exciting currents are supplied to cause the spindle motor to produce reverse torque in response to a control signal to sotp which is given when the spindle motor is rotating the rotary recording medium. Reversal of the direction of rotation of the spindle motor is detected and the supply of the exciting currents to the spindle motor interrupted in response to the detection signal.
When recording or reproducing is finished or suspended, a stop signal is produced. In response to the stop signal, the spindle motor produce reverse torque. The reverse torque is the deceleration torque which provides a large negative acceleration, and it is electrically produced. The spindle motor is quickly decelerated by the reverse torque. As soon as the spindle motor is stopped, the spindle motor begins to rotate in the opposite direction. However, at the instant when the motor begins rotating in the opposite direction, a detection signal is produced in response to interrupt the supply of the exciting current, as a result of which the spindle motor is stopped.
As is apparent from the above description, after the stop signal is provided, the inversion torque acts on the spindle motor until the latter is stopped. When the spindle motor begins rotating in the opposite direction, the torque becomes zero. Therefore, the spindle motor is positively and quickly stopped. Accordingly, when the rotary recording medium is removed from the spindle after recording or reproducing is finished or suspended, and the same or another rotary recording medium is loaded, the center core of the rotary recording medium is removed from or fitted on the spindle which is substantially stopped, and the center core pusher pushes a substantially stationary center core.